A signal transmitted through a wireless channel is distorted by the wireless channel. Accordingly, modulation/demodulation and encoding/decoding processes of data are performed to restore data from the distorted signal.
Examples of representative modulation/demodulation schemes used in current mobile communication systems include Mary-QAM (where M is 4, 16, 64, and 256), and examples of representative encoding schemes include an encoding scheme using a turbo code.
After turbo-encoded and Mary-QAM modulated signal is received to be Mary-QAM demodulated, the signal is decoded by a turbo decoder implemented in hardware such as FPGA or ASIC for decoding the demodulated signal.
Log Likelihood Ratio (LLR) data inputted from a demodulator is selected in consideration of hardware complexity and processing time of a turbo decoder. LLR data inputted from a related-art demodulator to a turbo decoder has a bit-width of 6 to 9 bits.
Bit-width of demodulated LLR signal has a significant effect on the complexity and the processing time upon implementation of turbo decoder hardware.
If the bit-width of inputted LLR data of a turbo decoder is small, data error rates increase. If the bit-width of the inputted LLR data is too big, hardware complexity and necessity for a higher processing speed increase.
When the bit-width of LLR data inputted from a demodulator according a modulation scheme applied for data transmission is maintained constant, performance might be deteriorated depending on a modulation scheme of a signal.
The present disclosure provides a method for restoring data without performance deterioration and increased complexity of a turbo decoder by varying a bit-width of operation data according to a modulation scheme, in regard to a decoding operation of LLR data inputted from a demodulator to a turbo decoder.